CVE-2026-105236 - Vulnerability Details

- TLS 1.2 session resumption in ssl crosses SNI virtual-host client-certificate trust boundaries

Description

Improper Certificate Validation vulnerability in the ssl application in Erlang/OTP allows a client that holds a certificate trusted by one SNI virtual host to authenticate to a second SNI virtual host on the same listener by resuming its TLS 1.2 session there.

A server that serves several SNI names from one listen socket through sni_fun or sni_hosts keeps one pre-TLS 1.3 session cache per listener and does not bind a cached session to the SNI name or client trust policy that established it. When an SNI option set switches to verify_peer without naming reuse_sessions, ssl_config:update_options/3 inherits the base listener's reuse_sessions value of true, so the default that disables reuse for client-authenticating servers does not apply. On an abbreviated handshake ssl_session:is_resumable/4 checks only that the cached session uses one of the current server certificates and carries some peer certificate, and never revalidates that certificate against the CA selected for the requested name. The names must share a server certificate, which is common with wildcard or multi-SAN certificates. TLS 1.3 does not use this cache and is not affected.

This issue affects OTP from OTP 18.0 before OTP 27.3.4.19, OTP 28.5.0.8, and OTP 29.1.2, corresponding to ssl from 7.0 before 11.2.12.14, 11.6.0.7, and 11.7.8.

Published: 2026-10-14

Score: 6.3 Medium

EPSS: < 1% Very Low

KEV: No

Impact:

Action:

Analysis

Impact

The vulnerability allows a client that holds a certificate trusted by one SNI virtual host to authenticate to a second SNI virtual host on the same listener by resuming a TLS 1.2 session. In effect, the ssl application in Erlang/OTP does not bind cached sessions to the SNI name or the CA policy that established them, enabling cross‑name session resumption. This weakness is an instance of improper certificate validation (CWE‑295). The attacker can masquerade as a valid client of a different service, potentially gaining unauthorized access to resources protected by the second service's client‑certificate authentication.

Affected Systems

The affected product is Erlang:OTP. All OTP releases prior to 27.3.4.19, as well as the specific releases 28.5.0.8 and 29.1.2, contain the vulnerability. The ssl libraries affected are versions 7.0 up to 11.2.12.14, 11.6.0.7, and 11.7.8. Users running these releases on a listener that serves multiple SNI names without separate session caches are at risk.

Risk and Exploitability

The CVSS score of 6.3 indicates a moderate impact. The EPSS score is < 1%, meaning the probability of exploitation is very low. The vulnerability is not listed in the CISA KEV catalog. The attack path requires a client with a certificate trusted by one SNI host to perform a TLS 1.2 handshake to the same listener for a different SNI name. The session‑resume check fails to re‑validate the peer certificate against the CA selected for the requested name, so an attacker can potentially gain authentication privileges to other virtual hosts over a single TLS listener.

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions

Erlang

OTP

unaffected

Version	Status	Constraints
`18.0`	affected	< *

Erlang

OTP

unaffected

Version	Status	Constraints
`7.0`	affected	< *

Erlang

OTP

unaffected

Version	Status	Constraints
`4fe38c4b8b2c8024afb60990e598ff823743fd54`	affected	< *

No data.

Vendor Product Confidence Versions

Erlang

Erlang/otp

95%

Version	Status	Scheme	Platform
`[18.0,27.3.4.19)`	affected	generic	—
`[27.3.4.19,28.5.0.8)`	unaffected	generic	—
`[28.5.0.8,29.1.2)`	unaffected	generic	—
`[29.1.2,*]`	unaffected	generic	—

Erlang

Erlang/otp

95%

Version	Status	Scheme	Platform
`[7.0,11.2.12.14)`	affected	generic	—
`[11.2.12.14,11.6.0.7)`	unaffected	generic	—
`[11.6.0.7,11.7.8)`	unaffected	generic	—
`[11.7.8,*]`	unaffected	semver	—

Erlang

Erlang/otp

95%

Version	Status	Scheme	Platform
`[4fe38c4b8b2c8024afb60990e598ff823743fd54,0c20f3683b3c81fd30b46047195be9b3d2c69d76)`	affected	code_commit	—
`[0c20f3683b3c81fd30b46047195be9b3d2c69d76,10ee925d0fee8413f1170cc21bfcf123c8d22454)`	unaffected	code_commit	—
`[10ee925d0fee8413f1170cc21bfcf123c8d22454,4d76adbf39d547a931048544df09c3c087e56618)`	unaffected	code_commit	—
`[4d76adbf39d547a931048544df09c3c087e56618,*]`	unaffected	code_commit	—

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Remediation

Vendor Workaround

* Set {reuse_sessions, false} in each SNI service's option set, or in the base listener options. The reporter's proof of concept confirmed that this blocks the cross-name resumption. * Serve distinct SNI trust domains on separate listen sockets, which gives each its own session cache. * Restrict the listener to TLS 1.3 with {versions, ['tlsv1.3']}. TLS 1.3 does not use the session-ID cache.

OpenCVE Recommended Actions

Upgrade Erlang/OTP to 27.3.4.19 or later (including OTP 28.5.0.8 and OTP 29.1.2).
Set {reuse_sessions,false} in each SNI service’s option set or in the base listener options to block cross‑name session resumption.
Serve distinct SNI trust domains on separate listen sockets so each domain has its own session cache.
Configure the listener to restrict the protocol to TLS 1.3 with {versions, ['tlsv1.3']}, which does not use the session‑ID cache.

Generated by OpenCVE AI on October 15, 2026 at 15:34 UTC.

Tracking

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Advisories

No advisories yet.

Attack Vector Network

Attack Complexity Low

Privileges Required None

Attack Requirements Present

User Interaction None

Vulnerable System Confidentiality Impact Low

Vulnerable System Integrity Impact Low

Vulnerable System Availability Impact None

Subsequent System Confidentiality Impact None

Subsequent System Integrity Impact None

Subsequent System Availability Impact None

Attack Vector Network

Attack Complexity High

Privileges Required None

Scope Unchanged

Confidentiality Impact Low

Integrity Impact Low

Availability Impact None

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

The EPSS score is 0.00357.

Exploitation none

Automatable no

Technical Impact partial

References

Link	Providers
https://cna.erlef.org/cves/CVE-2026-105236.html
https://github.com/erlang/otp/commit/0c20f3683b3c81fd30b46047195be9b3d2c69d76
https://github.com/erlang/otp/commit/10ee925d0fee8413f1170cc21bfcf123c8d22454
https://github.com/erlang/otp/commit/4d76adbf39d547a931048544df09c3c087e56618
https://github.com/erlang/otp/commit/4fe38c4b8b2c8024afb60990e598ff823743fd54
https://github.com/erlang/otp/security/advisories/GHSA-2g23-cgjh-34gq
https://nvd.nist.gov/vuln/detail/CVE-2026-105236
https://osv.dev/vulnerability/EEF-CVE-2026-105236
https://www.cve.org/CVERecord?id=CVE-2026-105236
https://www.erlang.org/doc/system/versions.html#order-of-versions

History

Fri, 23 Oct 2026 00:45:00 +0000

Type	Values Removed	Values Added
First Time appeared		Erlang erlang/otp
Vendors & Products		Erlang erlang/otp

Tue, 20 Oct 2026 00:30:00 +0000

Type	Values Removed	Values Added
References		https://nvd.nist.gov/vuln/detail/CVE-2026-105236 https://www.cve.org/CVERecord?id=CVE-2026-105236
Metrics	threat_severity `None`	cvssV3_1 `{'score': 4.8, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N'}` threat_severity `Moderate`

Fri, 16 Oct 2026 21:30:00 +0000

Type	Values Removed	Values Added
Metrics		ssvc `{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}`

Wed, 14 Oct 2026 17:00:00 +0000

Type	Values Removed	Values Added
Description		Improper Certificate Validation vulnerability in the ssl application in Erlang/OTP allows a client that holds a certificate trusted by one SNI virtual host to authenticate to a second SNI virtual host on the same listener by resuming its TLS 1.2 session there. A server that serves several SNI names from one listen socket through sni_fun or sni_hosts keeps one pre-TLS 1.3 session cache per listener and does not bind a cached session to the SNI name or client trust policy that established it. When an SNI option set switches to verify_peer without naming reuse_sessions, ssl_config:update_options/3 inherits the base listener's reuse_sessions value of true, so the default that disables reuse for client-authenticating servers does not apply. On an abbreviated handshake ssl_session:is_resumable/4 checks only that the cached session uses one of the current server certificates and carries some peer certificate, and never revalidates that certificate against the CA selected for the requested name. The names must share a server certificate, which is common with wildcard or multi-SAN certificates. TLS 1.3 does not use this cache and is not affected. This issue affects OTP from OTP 18.0 before OTP 27.3.4.19, OTP 28.5.0.8, and OTP 29.1.2, corresponding to ssl from 7.0 before 11.2.12.14, 11.6.0.7, and 11.7.8.
Title		TLS 1.2 session resumption in ssl crosses SNI virtual-host client-certificate trust boundaries
First Time appeared		Erlang Erlang erlang\/otp
Weaknesses		CWE-295
CPEs		cpe:2.3:a:erlang:erlang\/otp::::::::
Vendors & Products		Erlang Erlang erlang\/otp
References		https://cna.erlef.org/cves/CVE-2026-105236.html https://github.com/erlang/otp/commit/0c20f3683b3c81fd30b46047195be9b3d2c69d76 https://github.com/erlang/otp/commit/10ee925d0fee8413f1170cc21bfcf123c8d22454 https://github.com/erlang/otp/commit/4d76adbf39d547a931048544df09c3c087e56618 https://github.com/erlang/otp/commit/4fe38c4b8b2c8024afb60990e598ff823743fd54 https://github.com/erlang/otp/security/advisories/GHSA-2g23-cgjh-34gq https://osv.dev/vulnerability/EEF-CVE-2026-105236 https://www.erlang.org/doc/system/versions.html#order-of-versions
Metrics		cvssV4_0 `{'score': 6.3, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N'}`

Subscriptions

Erlang Erlang/otp Erlang\/otp

MITRE

Status: PUBLISHED

Assigner: EEF

Published: 2026-10-14T16:55:51.495Z

Updated: 2026-10-16T20:09:49.566Z

Reserved: 2026-10-08T14:45:01.411Z

Link: CVE-2026-105236

Vulnrichment

Updated: 2026-10-16T20:09:38.315Z

NVD

Status : Deferred

Published: 2026-10-14T17:18:14.720

Modified: 2026-10-16T21:17:15.680

Link: CVE-2026-105236

Redhat

Severity : Moderate

Publid Date: 2026-10-14T16:55:51Z

Links: CVE-2026-105236 - Bugzilla

OpenCVE Enrichment

Updated: 2026-10-22T22:30:12Z

Weaknesses

CWE-295
Improper Certificate Validation

Impact

Affected Systems

Risk and Exploitability

Tracking

Attack Vector Network

Attack Complexity Low

Privileges Required None

Attack Requirements Present

User Interaction None

Vulnerable System Confidentiality Impact Low

Vulnerable System Integrity Impact Low

Vulnerable System Availability Impact None

Subsequent System Confidentiality Impact None

Subsequent System Integrity Impact None

Subsequent System Availability Impact None

Attack Vector Network

Attack Complexity High

Privileges Required None

Scope Unchanged

Confidentiality Impact Low

Integrity Impact Low

Availability Impact None

User Interaction None

Exploitation none

Automatable no

Technical Impact partial

Subscriptions

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